December 18, 2017. Difficulty rose by +17.74% to 1.87T from 1.59T.
Change
+17.74%
New difficulty
1.87T
Period length
11.9 days
Network hashrate then (7-day)
13.8 EH/s
Bitcoin price then
$18,286
Hashprice then
$2,340/PH/day
The 2,016 blocks before it took 11.9 days instead of 14, so the network had more hashrate than the difficulty assumed, and difficulty rose by 17.74%: one of the largest adjustments on record. For every machine on the network that is a pay cut of the same size until the next retarget.